The present invention relates to non-contact fluid transfer methods, apparatus and uses thereof
Many methods for the precision transfer and handling of fluids are known and used in a variety of commercial and industrial applications. The presently burgeoning industries of biotechnology and biopharmaceuticals are particularly relevant examples of industries requiring ultra-pure fluid handling and transfer techniques. Not only is purity a concern, current biotechnological screening and manufacturing methods also require high throughput to efficiently conduct screening of compound libraries, synthesis of screening components, and the like.
Current fluid transfer methods require contacting the fluid with a transfer device, e.g., a pipette, a pin, or the like. Such contact methods dramatically increase the likelihood of contamination. Many biotechnology procedures, e.g., polymerase chain reaction (PCR), have a sensitivity that results in essentially a zero tolerance for contamination. Accordingly, a non-contact method for fluid transfer would result in a drastic reduction in opportunities for sample contamination.
Current biotechnology screening techniques may involve many thousands of separate screening operations, with the concomitant need for many thousands of fluid transfer operations in which small volumes of fluid are transferred from a fluid source (e.g., a multi-well plate comprising, for example, a library of test compounds) to a target (e.g., a site where a test compound is contacted with a defined set of components). Thus, not only the source, but also the target may comprise thousands of loci that need to be accessed in a rapid, contamination-free manner.
Similarly, biotechnology synthesis methods for the generation of tools useful for conducting molecular biology research often require many iterations of a procedure that must be conducted without contamination and with precision. For example, oligonucleotides of varying lengths are tools that are commonly employed in molecular biology research applications, as, for example, probes, primers, anti-sense strands, and the like. Traditional synthesis techniques comprise the stepwise addition of a single nucleotide at a time to a growing oligomer strand. Contamination of the strand with an erroneously placed nucleotide renders the oligonucleotide useless. Accordingly, a non-contact method for transferring nucleotides to the reaction site of a growing oligomer would reduce the opportunity for erroneous transfer of an unwanted nucleotide that might otherwise contaminate a pipette or other traditional contact-based transfer device.
Furthermore, existing fluid transfer methods are limited, and do not conveniently and reliably produce the high efficiency, high-density arrays. Such arrays are also useful in conducting screening, synthesis, and other techniques commonly used in biotechnology.
Accordingly, there exists a need in the art for a non-contact method for the precision transfer of small amounts of fluid in a rapid manner that is easily automated to meet industry needs.
In order to overcome the deficiencies of the prior art, the present invention provides non-contact methods for the transfer of small amounts of fluid. Methods according to the present invention employ the use of acoustic waves to generate micro-droplets of fluid. In the methods, acoustic waves are propagated through a pool of a source fluid to cause the ejection of at least one, e.g., a single micro-droplet, from the surface of the pool. The droplet is ejected towards a target with sufficient force to provide for contact of the droplet with the target.
The methods of the invention are easily automated in a manner that provides for the processing of many different sources of fluid from an array of pools of source fluid, and further provides for an array of target sites to receive the micro-droplets of source fluid as they are ejected from the pools of source fluid. In this manner thousands of individual samples of source fluid can be processed and directed to the same or two or more (e.g., a thousands or more) separate target sites for further reaction, detection, and the like. Thus, the present invention, because of its non-contact methodology, not only has greater intrinsic reliability than is provided by presently available liquid ejection on demand and continuous stream piezoelectric type pumps, but also is compatible with a wider variety of liquid compounds, including liquid compounds which have relatively high viscosity and liquid compounds which contain particulate components.
The invention provides a non-contact method for transferring small amounts of source fluid to a target, said method comprising propagating an acoustic wave from an acoustic liquid deposition emitter through a source fluid containment structure into a pool of source fluid, wherein said acoustic liquid deposition emitter is in contact with said source fluid containment structure typically through a coupling medium which is interposed between said acoustic liquid deposition emitter and a first surface of said source fluid containment structure, said pool of source fluid is on a second surface of said source fluid containment structure that is opposite or adjacent to said acoustic liquid deposition emitter, and said acoustic wave causes controlled ejection of at least one droplet of said source fluid from said pool to said target.
The invention also provides a non-contact method for transferring small amounts of a source fluid to a separate target structure, said method comprising activating a piezoelectric transducer thereby propagating an acoustic wave through a coupling medium which is interposed between said piezoelectric transducer and a first surface of a source fluid containment structure, wherein said source fluid is contained on a second surface of said source fluid containment structure that is opposite said piezoelectric transducer, and said target is positioned to receive a droplet of fluid ejected from said source fluid as a result of propagation of said acoustic wave through said source fluid.
The invention further provides a method for transferring small amounts of a source fluid from a pool selected from one of a plurality of pools of source fluid located on a first surface of a source fluid containment structure, to a separate target structure without physically contacting said source fluid, said method comprising propagating an acoustic wave through said source fluid such that a single droplet of fluid is ejected from the surface of said pool of source fluid with sufficient energy to bring said droplet into contact with said target, wherein said acoustic wave is propagated from a piezoelectric transducer, said piezoelectric transducer is in contact, opposite to, or adjacent with said source fluid containment structure via a coupling medium interposed between said piezoelectric transducer and a second surface of said source fluid containment structure, said second surface of said source fluid containment structure is opposite said pool of source fluid, and said target is opposite or adjacent to said surface of said pool of source fluid.
The invention also provides an apparatus for performing non-contact transfer of small amounts of source fluid. The apparatus includes an acoustic liquid deposition emitter and a stage wherein the stage is configured to support a source fluid containment structure supported such that the acoustic liquid deposition emitter is in operative contact with the source fluid containment structure when a coupling medium is interposed there between. The apparatus may include a number of additional elements, including, for example: an acoustic wave channel structure that is mechanically coupled to the acoustic liquid deposition emitter (e.g., a piezoelectric transducer) to provide for transmission of an acoustic wave from, e.g., the piezoelectric transducer to said coupling medium; a structure for maintaining the coupling medium in operative contact with the acoustic liquid deposition emitter; a lens for focusing said acoustic wave; controls for varying one or more of frequency, voltage, and duration of an energy source used to excite the acoustic liquid deposition emitter and thereby propagate an acoustic wave; a stage actuator for user-defined positioning of the stage relative to the acoustic liquid deposition emitter; a focussing actuator for user-defined positioning of said acoustic liquid deposition emitter relative to said stage; a computer for controlling the stage actuator and/or the focussing actuator; and a fluid level detector for detecting a level of fluid in a source fluid containment structure supported by said stage.
The invention also provides a system for performing non-contact transfer of small amounts of a source fluid. The system includes a source fluid containment structure, a movable stage configured to support the source fluid containment structure, an acoustic liquid deposition emitter in operative contact with the source fluid containment structure, a coupling medium interposed between the deposition emitter and the source fluid containment structure, and a computer in operable communication with the acoustic liquid deposition emitter for varying one or more of frequency, voltage and duration of an energy source used to excite the acoustic liquid deposition emitter and wherein the computer is in communication with the movable stage for positioning the source fluid such that operative contact with the acoustic liquid deposition emitter.